JSFiddle - React, Tailwind, and code Playground

JavaScript

const MyFunctionClass = function(str) {
	this.str = str;
}

MyFunctionClass.prototype.sayHi = function() {
	console.log("Hi from fuction! --" + this.str)
}

const myFunctionInstnace = new MyFunctionClass("foo");
myFunctionInstnace.sayHi();
// Reset
MyFunctionClass.apply(myFunctionInstnace, ["bar"]);
myFunctionInstnace.sayHi();


// Classes:
class MyClassClass {
	constructor(str) {
  	this.str = str;
  }
	sayHi() {
  		console.log("Hi from class! --" + this.str)
  }
}

const myClassInstnace = new MyClassClass("foo");
myClassInstnace.sayHi();
// Reset
  MyClassClass.apply(myClassInstnace, ["bar"]); // Uncomment for error
myClassInstnace.sayHi();